The present invention relates to a vibration generating unit and more particularly to a vibration generating unit applicable to, e.g., a handy phone or a radio pager and capable of reducing irregularity in bodily sensed vibration.
A handy phone or a radio pager, for example, often includes a vibration type alerting unit usually implemented by a vibration motor. However, the problem with this type of alerting unit is that each vibration motor has a particular rotation speed and therefore a particular amount of vibration. Vibration available with the vibration motor is sometimes short. The vibration type alerting device has been proposed in various forms in the past, as follows.
(1) Japanese Utility Model Publication No. 2571811 proposes an alerting unit applicable to a radio pager or a handy phone and outputting both of vibration and sound. However, this alerting unit is not directed toward the stabilization of the amount of vibration.
(2) Japanese Utility Model Laid-Open Pub Ii cat ion No. 2-88346 teaches an actuator built in a radio pager for producing an alert. The actuator includes a miniature motor and an eccentric weight mounted on the output shaft of the motor. The actuator does not use an electromagnetic force.
(3) Japanese Patent Laid-Open Publication No. 4-3630 discloses a vibration generating unit for a radio pager. The unit includes an elongate, flat affixing plate and a vibration plate facing the affixing plate and connected at one end to one end of the affixing plate. An armature for generating an electromagnetic force is affixed to one of the facing portions of the affixing plate and vibration plate. A permanent magnet having either the North Pole or the South Pole is affixed to the other of the above two facing portions and located to face the armature. Means is provided for intermittently feeding a current to the armature. Although the device uses an electromagnetic force, the electromagnetic force is not directed toward the stabilization of the amount of vibration.
(3) Japanese Patent Laid-Open Publication No. 6-311693 proposes a flat vibration generating device applicable to, e.g., a pager and resembling a button type battery. This device also uses a vibration motor, but does not use an electromagnetic force.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 10-215499, 8-294260, 9-205763, and 10-258253.